Hi nzcassie, welcome to Cruise-Chat! It's about 35 miles from the airport to the port. There are a few shuttle services out there. I Googled transportation from Santa Ana to Port of Los Angeles and got quite a few hits. It looked like it was around $55 for most of the companies I clicked on the links to.

I just got a quote of $37 for the first passenger and $9 for each additional, or $46 for two for Super Shuttle from the Port of Long Beach to SNA (John Wayne).

Penny, the Port of Los Angeles is in San Pedro; the Port of Long Beach is actually a little closer to Santa Ana. It looks like one big port from the air, but is actually two. Carnival ports in Long Beach.